With the increasing cost of precious metals, such as silver, gold, etc. added effort has been placed in the development of systems for recovering precious metals from solutions after the metals have been employed in a particular process. Typically such systems have found general acceptance in photography where silver salts are employed in the development process and remain in the spent photographic developing solution.
Although interest in recovering precious metals from these various solutions has long existed, most of the prior art systems require chemical reactions with the solutions in order to precipitate the precious metal from the solution, and thereby obtain its recovery. However, such processes are undesirable, due to the additional effort required by the user. Typically, the user must carefully measure various precise amounts of reaction-inducing chemicals, mix the chemicals into the precious metal-bearing solution and then conduct various processing steps to obtain the desired recovery.
In order to eliminate these undesirable chemical reaction recovery systems, some prior art filtration systems were developed. However, all of these prior art systems are costly and are usually heavy and complex to operate. In addition, many of these systems employ a chemically reactive filter that must be carefully watched to assure its proper operation.
One non-reactive filtration system is disclosed in my own U.S. Pat. No. 4,371,436. As disclosed therein, a multiple filter system is used wherein the liquid containing the precious metal is gravity fed through a plurality of non-reactive filter elements which removes finer and finer sized silver particles from the solution, with the fully filtered solution being delivered to a waste drainage port.
Although this prior art system does achieve a non-reactive filtration of precious metals from their solution, the complexity of this system is undesirable. In particular, a plurality of various filter elements are required, with each of the filter elements having progressively smaller micron sizes in order to achieve the desired result. Consequently, a plurality of various different size filter elements must be maintained in stock and must be inserted into the system in the proper sequence in order to keep the system operating correctly. Furthermore, it has been found that complete passage of the solution through the finer filter elements is not always achieved smoothly and effectively.
Consequently, it is a principal object of the present invention to provide precious metal recovery apparatus which effectively and efficiently filters precious metal from substantially all liquid solution, without requiring a reaction of the solution with chemicals or with the filter system.
Another object of the present invention is to provide precious metal recovery apparatus having the characteristic features described above which employs a single filter which is easily positioned in the recovery apparatus and quickly and easily removed therefrom when the desired filtration has been achieved.
Another object of the present invention is to provide precious metal recovery apparatus having the characteristic features described above which is easily used by untrained personnel, as well as highly portable and uncomplicated.
Another object of the present invention is to provide precious metal recovery apparatus having the characteristic features described above which is highly reliable, while also providing efficient and effective substantially complete filtration and retention of the desired precious metal.
Other and more specific objects will in part be obvious and will in part appear hereinafter.